1. Field of the Invention
This invention relates to a method of preparing a graphene oxide/rubber nanocomposite which has high delamination degree, high dispersion degree, and strong interfacial boding action, particularly to a method of preparing a graphene oxide/rubber nanocomposite contaning a surfactant made by emulsion compounding with flocculation process or by emulsion compounding with spray drying process.
2. Description of the Related Art
In rubber industry, the most widely used fillers are nano sized carbon black and white carbon black. Carbon black is the most important reinforcing fillers for rubber industry. However, as the petroleum resources are running out, carbon black industry which absolutely relies upon petroleum industry is restricted. In addition, the production and application of carbon black cause environment pollution. The reinforcing property of white carbon black to rubber is close to that of carbon black to rubber. However, rubber filled by white carbon black has weaknesses. Particularly, during production, it's hard to mix white carbon black with rubber. Once carbon black does not evenly disperse in rubber, the rubber exhibits low intensity and poor property. Submicron sized and micron sized non-metallic mineral materials are also used as fillers in rubber industry, and the most widely used materials are ceramics and calcium carbonate, dolomite, aedelforsite, talcum, cryolite, pyrophillite, and barite. These fillers are used for the purpose of reducing cost, and do not contribute to the intensity of rubber. Therefore, it is one objective to develop new reinforcing fillers (low consumed, environmental friendly, and free of petroleum resources) to replace conventional fillers and to provide an efficient, convenient, and economic method in rubber industry.
Graphene is a hexagonal flat film of carbon atoms formed by sp2 hybrid orbitals, and is a two dimensional material at a length of one or several carbon atoms. In 2004, Novoselov and Geim from the University of Manchester prepared self-existent two dimensional graphene crystals for the first time by using a tape to delaminate highly oriented graphite. Since graphene has infinite periodically repeated structures in a flat surface and has a nano sized length in a direction perpendicular to the flat surface, graphene can be regarded as a nano material having a macro size. Graphene has a high specific area in theory (about 2630 m2/g), large aspect ratio (>1000), and excellent mechanical strength (Young's modulus of graphene is 1060 GPa). Therefore, graphene exhibits potential advantages for efficient reinforcement of polymer materials.
Structurally complete graphene has high chemical stability. The surface of structurally complete graphene is inert, and the interactions between structurally complete graphene and other medium (such as a solvent) are weak. Van Der Waals force between different sheets of graphene is strong, and thus, graphene powders are prone to aggregate and are hard to dissolve in water or common organic solvents. This causes great difficulties for preparing graphene/polymer composites. Reducing graphite oxide is the mostly widely used method for preparing graphene. Graphite oxide is an intermediate during the process of reducing graphite oxide to produce graphene. Graphite oxide is completely delaminated and changes into graphene oxide by a process of dispersing graphite oxide in water or organic solvent and further processing graphite oxide by ultrasonic waves. There are many oxygen functional groups on the surface of graphene oxide so that graphene oxide is compatible with water and common organic solvents, Van Der Waals force between different sheets of graphene oxide is weakened, and aggregation degree is reduced. Until now, graphene oxide has been used as a reinforcing filler and has been successfully dispersed into polymers having hard plastic substrate (such as polyvinyl acetate, polymethyl methacrylate, and polycaprolactone). (Xu, Y.; Hong, W; Bai, H.; Li, C.; Shi, G Carbon 2009, 47, 3538-3543. Liang, J.; Huang, Y.; Zhang, L.; Wang, Y.; Ma, Y.; Guo, T.; Chen, Y. Adv, Funct. Mater. 2009, 19, 2297-2302. Jang, J. Y.; Kim, M. S.; Jeong, H. M.; Shin, C. M. Compos. Sci. Technol. 2009, 69, 186-191. Kai, W.; Hirota, Y.; Hua, L.; Inoue, Y. J. Appl. Polym. Sci. 2008, 107, 1395-1400. Cai, D.; Song, M. Nanotechnology 2009, 20, 315708/1-315708/6). However, it's a pity that advanced preparation technology which efficiently composites graphene oxide and rubber (simple, easy to industrialize, and obtaining a product having good properties) was not reported as yet. The preparation of excellent rubber products relies upon the solution to dispersion of graphene oxide in rubber and interfacial bonding between graphene oxide and rubber.